U.S. patent application number 13/143187 was filed with the patent office on 2012-11-29 for writing data to sub-pixels using different write sequences.
This patent application is currently assigned to Apple Inc.. Invention is credited to Hopil Bae, Shih Chang Chang, Zhibing Ge, Cheng Ho Yu.
Application Number | 20120299983 13/143187 |
Document ID | / |
Family ID | 44462128 |
Filed Date | 2012-11-29 |
United States Patent
Application |
20120299983 |
Kind Code |
A1 |
Chang; Shih Chang ; et
al. |
November 29, 2012 |
WRITING DATA TO SUB-PIXELS USING DIFFERENT WRITE SEQUENCES
Abstract
With respect to liquid crystal display inversion schemes, a
large change in voltage on a data line can affect the voltages on
adjacent data lines due to capacitive coupling between data lines.
The resulting change in voltage on these adjacent data lines can
give rise to visual artifacts in the data lines' corresponding
sub-pixels. Various embodiments of the present disclosure serve to
prevent or reduce persisting visual artifacts by offsetting their
effects or by distributing their presence among different colored
sub-pixels. In some embodiments, this may be accomplished by using
different write sequences during the update of a row of pixels.
Inventors: |
Chang; Shih Chang; (San
Jose, CA) ; Yu; Cheng Ho; (Cupertino, CA) ;
Ge; Zhibing; (Sunnyvale, CA) ; Bae; Hopil;
(Sunnyvale, CA) |
Assignee: |
Apple Inc.
|
Family ID: |
44462128 |
Appl. No.: |
13/143187 |
Filed: |
May 24, 2011 |
PCT Filed: |
May 24, 2011 |
PCT NO: |
PCT/US11/37810 |
371 Date: |
July 1, 2011 |
Current U.S.
Class: |
345/691 ;
345/208; 345/209 |
Current CPC
Class: |
G09G 2320/0209 20130101;
G09G 2320/0233 20130101; G09G 3/3614 20130101; G09G 3/3688
20130101; G09G 2300/0876 20130101; G09G 2310/0297 20130101; G09G
3/3659 20130101; G09G 2310/0218 20130101 |
Class at
Publication: |
345/691 ;
345/208; 345/209 |
International
Class: |
G09G 5/10 20060101
G09G005/10; G06F 3/038 20060101 G06F003/038 |
Claims
1. A method of scanning a display, the display including a
plurality of display pixels that are each associated with a set of
a plurality of data lines, comprising: electrically connecting each
display pixel in a line of the display pixels to the associated set
of data lines during an update of the line of display pixels, the
line of display pixels including a first display pixel associated
with a first set of data lines and a second display pixel
associated with a second set of data lines; sequentially applying
voltages to the first set of data lines in a first write sequence
of the data lines during the update of the line of display pixels;
and sequentially applying voltages to the second set of data lines
in a second sequence of the data lines, different than the first
write sequence, during the update of the line of display
pixels.
2. The method of claim 1, wherein each set of data lines includes a
left data line, a center data line, and a right data line.
3. The method of claim 2, wherein sequentially applying voltages to
the first set includes applying a first voltage to the center data
line in the first set, and sequentially applying voltages to the
second set includes applying a second voltage to the center data
line in the second set, the second voltage being applied
concurrently with the application of the first voltage.
4. The method of claim 3, wherein the left data line is a red data
line, the center data line is a green data line, the right data
line is a blue data line, the first write sequence is a
green-blue-red write sequence, and the second write sequence is a
green-red-blue write sequence.
5. The method of claim 1, wherein the first and second display
pixels are adjacent, sequentially applying voltages to the first
set includes applying a first voltage to a first data line in the
first set, and sequentially applying voltages to the second set
includes applying a second voltage to a second data line in the
second set, the second voltage being applied concurrently with the
application of the first voltage, and the first and second data
lines being adjacent data lines.
6. The method of claim 1, wherein the first write sequence and
second write sequence form a pattern that is repeated in adjacent
pairs of display pixels.
7. The method of claim 1, wherein the first set includes a first
data line, a second data line, and a third data line, the first
data line being adjacent to each of the second and third data
lines, and wherein sequentially applying voltages to the first set
includes applying a first voltage to the first data line, applying
a second voltage to the second data line such that a voltage value
of the second data line changes from a positive polarity to a
negative polarity, and applying a third voltage to the third data
line such that a voltage value of the third data line changes from
a negative polarity to a positive polarity, the application of the
first voltage being prior to the application of each of the second
and third voltages.
8. The method of claim 1, wherein the first set includes a first
data line and a second data line, the first data line being
adjacent to the second data line, the second set includes a third
data line, the third data line being adjacent to the first data
line, and wherein sequentially applying voltages to the first set
includes applying a first voltage to the first data line, applying
a second voltage to the second data line such that the polarity of
a voltage value of the second data line changes, and sequentially
applying voltages to the second set includes applying a third
voltage to the third data line such that the polarity of a voltage
value of the third data line changes, the application of the first
voltage being prior to the application of each of the second and
third voltages, the second voltage having a polarity that is
opposite the polarity of the third voltage.
9. The method of claim 1, wherein the first and second display
pixels are adjacent, the first set includes a first data line and a
second data line, the first and second data lines being adjacent to
each other, and the second set includes a third data line and a
fourth data line, the third and fourth data lines being adjacent to
each other, and wherein sequentially applying voltages to the first
set includes applying a first voltage to the first data line, and
applying a second voltage to the second data line after the
application of the first voltage, the application of the second
voltage changing the polarity of a voltage value of the second data
line, the polarity of the second voltage being the same as the
polarity of the first voltage, and sequentially applying voltages
to the second set includes applying a third voltage to the third
data line, and applying a fourth voltage to the fourth data line
after the application of the third voltage, the application of the
fourth voltage changing the polarity of a voltage value of the
fourth data line, the polarity of the fourth voltage being opposite
of the polarity of the third voltage.
10. The method of claim 1, wherein the line of display pixels
further includes a third display pixel associated with a third set
of data lines and a fourth display pixel associated with a fourth
set of data lines, the method further comprising: sequentially
applying voltages to the third set of data lines in a third write
sequence of the data lines during the update of the line of display
pixels; and sequentially applying voltages to the fourth set of
data lines in a fourth write sequence of the data lines, during the
update of the line of display pixels, wherein the each of the
first, second, third, and fourth write sequences are different from
each other.
11. The method of claim 10, wherein each set of data lines includes
a left data line, a center data line, and a right data line.
12. The method of claim 11, wherein the first write sequence is a
red-green-blue write sequence, the second write sequence is a
blue-green-red write sequence, the third write sequence is a
blue-red-green write sequence, and the fourth write sequence is a
red-blue-green write sequence.
13. A non-transitory computer-readable storage medium storing
computer-readable instructions that, when executed by a computing
device, cause the device to perform a method of scanning a display,
the display including a plurality of display pixels that are each
associated with a set of a plurality of data lines, the method
comprising: electrically connecting each display pixel in a line of
the display pixels to the associated set of data lines during an
update of the line of display pixels, the line of display pixels
including a first display pixel associated with a first set of data
lines and a second display pixel associated with a second set of
data lines; sequentially applying voltages to the first set of data
lines in a first write sequence of the data lines during the update
of the line of display pixels; and sequentially applying voltages
to the second set of data lines in a second sequence of the data
lines, different than the first write sequence, during the update
of the line of display pixels.
14. The non-transitory computer-readable storage medium of claim
13, wherein each set of data lines includes a left data line, a
center data line, and a right data line, and wherein sequentially
applying voltages to the first set includes applying a first
voltage to the center data line in the first set, and sequentially
applying voltages to the second set includes applying a second
voltage to the center data line in the second set, the second
voltage being applied concurrently with the application of the
first voltage.
15. The non-transitory computer-readable storage medium of claim
13, wherein the first and second display pixels are adjacent, and
sequentially applying voltages to the first set includes applying a
first voltage to a first data line in the first set, and
sequentially applying voltages to the second set includes applying
a second voltage to a second data line in the second set, the
second voltage being applied concurrently with the application of
the first voltage, and the first and second data lines being
adjacent data lines.
16. The non-transitory computer-readable storage medium of claim
13, wherein the first write sequence and second write sequence form
a pattern that is repeated in adjacent pairs of display pixels.
17. The non-transitory computer-readable storage medium of claim
13, wherein the first set includes a first data line, a second data
line, and a third data line, the first data line being adjacent to
each of the second and third data lines, and wherein sequentially
applying voltages to the first set includes applying a first
voltage to the first data line, applying a second voltage to the
second data line such that a voltage value of the second data line
changes from a positive polarity to a negative polarity, and
applying a third voltage to the third data line such that a voltage
value of the third data line changes from a negative polarity to a
positive polarity, the application of the first voltage being prior
to the application of each of the second and third voltages.
18. The non-transitory computer-readable storage medium of claim
13, wherein the first set includes a first data line and a second
data line, the first data line being adjacent to the second data
line, the second set includes a third data line, the third data
line being adjacent to the first data line, and wherein
sequentially applying voltages to the first set includes applying a
first voltage to the first data line, applying a second voltage to
the second data line such that the polarity of a voltage value of
the second data line changes, and sequentially applying voltages to
the second set includes applying a third voltage to the third data
line such that the polarity of a voltage value of the third data
line changes, the application of the first voltage being prior to
the application of each of the second and third voltages, the
second voltage having a polarity that is opposite the polarity of
the third voltage.
19. The non-transitory computer-readable storage medium of claim
13, wherein the first and second display pixels are adjacent, the
first set includes a first data line and a second data line, the
first and second data lines being adjacent to each other, and the
second set includes a third data line and a fourth data line, the
third and fourth data lines being adjacent to each other, and
wherein: sequentially applying voltages to the first set includes
applying a first voltage to the first data line, and applying a
second voltage to the second data line after the application of the
first voltage, the application of the second voltage changing the
polarity of a voltage value of the second data line, the polarity
of the second voltage being the same as the polarity of the first
voltage; and sequentially applying voltages to the second set
includes applying a third voltage to the third data line, and
applying a fourth voltage to the fourth data line after the
application of the third voltage, the application of the fourth
voltage changing the polarity of a voltage value of the fourth data
line, the polarity of the fourth voltage being opposite of the
polarity of the third voltage.
20. The non-transitory computer-readable storage medium of claim
13, wherein the line of display pixels further includes a third
display pixel associated with a third set of data lines and a
fourth display pixel associated with a fourth set of data lines,
the method further comprising: sequentially applying voltages to
the third set of data lines in a third write sequence of the data
lines during the update of the line of display pixels; and
sequentially applying voltages to the fourth set of data lines in a
fourth write sequence of the data lines, during the update of the
line of display pixels, wherein the each of the first, second,
third, and fourth write sequences are different from each
other.
21. A display apparatus, comprising: a display including a
plurality of display pixels that are each associated with a set of
a plurality of data lines; and a processor programmed for scanning
the display by electrically connecting each display pixel in a line
of the display pixels to the associated set of data lines during an
update of the line of display pixels, the line of display pixels
including a first display pixel associated with a first set of data
lines and a second display pixel associated with a second set of
data lines, sequentially applying voltages to the first set of data
lines in a first write sequence of the data lines during the update
of the line of display pixels, and sequentially applying voltages
to the second set of data lines in a second sequence of the data
lines, different than the first write sequence, during the update
of the line of display pixels.
22. The display apparatus of claim 21, wherein each set of data
lines in the display includes a left data line, a center data line,
and a right data line, and wherein the processor is further
programmed for sequentially applying voltages to the first set
includes applying a first voltage to the center data line in the
first set, and sequentially applying voltages to the second set
includes applying a second voltage to the center data line in the
second set, the second voltage being applied concurrently with the
application of the first voltage.
23. The display apparatus of claim 21, wherein the first and second
display pixels are adjacent, and wherein the processor is further
programmed for sequentially applying voltages to the first set by
applying a first voltage to a first data line in the first set, and
sequentially applying voltages to the second set by applying a
second voltage to a second data line in the second set, the second
voltage being applied concurrently with the application of the
first voltage, and the first and second data lines being adjacent
data lines.
24. The display apparatus of claim 21, wherein the first write
sequence and second write sequence form a pattern that is repeated
in adjacent pairs of display pixels.
25. The display apparatus of claim 21, wherein the first set
includes a first data line, a second data line, and a third data
line, the first data line being adjacent to each of the second and
third data lines, and wherein the processor is further programmed
for sequentially applying voltages to the first set by applying a
first voltage to the first data line, applying a second voltage to
the second data line such that a voltage value of the second data
line changes from a positive polarity to a negative polarity, and
applying a third voltage to the third data line such that a voltage
value of the third data line changes from a negative polarity to a
positive polarity, the application of the first voltage being prior
to the application of each of the second and third voltages.
Description
FIELD OF THE DISCLOSURE
[0001] This relates generally to the writing of data to sub-pixels
in display screens.
BACKGROUND OF THE DISCLOSURE
[0002] Display screens of various types of technologies, such as
liquid crystal displays (LCDs), organic light emitting diode (OLED)
displays, etc., can be used as screens or displays for a wide
variety of electronic devices, including such consumer electronics
as televisions, computers, and handheld devices (e.g., cellular
telephones, audio and video players, gaming systems, and so forth).
LCD devices, for example, typically provide a flat display in a
relatively thin package that is suitable for use in a variety of
electronic goods. In addition, LCD devices typically use less power
than comparable display technologies, making them suitable for use
in battery-powered devices or in other contexts where it is
desirable to minimize power usage.
[0003] LCD devices typically include multiple picture elements
(pixels) arranged in a matrix. The pixels may be driven by scanning
line and data line circuitry to display an image on the display
that can be periodically refreshed over multiple image frames such
that a continuous image may be perceived by a user. Individual
pixels of an LCD device can permit a variable amount light from a
backlight to pass through the pixel based on the strength of an
electric field applied to the liquid crystal material of the pixel.
The electric field can be generated by a difference in potential of
two electrodes, a common electrode and a pixel electrode. In some
LCDs, such as electrically-controlled birefringence (ECB) LCDs, the
liquid crystal can be in between the two electrodes. In other LCDs,
such as in-plane switching (IPS) and fringe-field switching (FFS)
LCDs, the two electrodes can be positioned on the same side of the
liquid crystal. In many displays, the direction of the electric
field generated by the two electrodes can be reversed periodically.
For example, LCD displays can scan the pixels using various
inversion schemes, in which the polarities of the voltages applied
to the common electrodes and the pixel electrodes can be
periodically switched, i.e., from positive to negative, or from
negative to positive. As a result, the polarities of the voltages
applied to various lines in a display panel, such as data lines
used to charge the pixel electrodes to a target voltage, can be
periodically switched according to the particular inversion
scheme.
SUMMARY
[0004] With respect to liquid crystal display inversion schemes, a
large change in voltage on a data line can affect the voltages on
adjacent data lines due to capacitive coupling between data lines.
The resulting change in voltage on these adjacent data lines can
give rise to visual artifacts in the data lines' corresponding
sub-pixels. However, not all sub-pixels will have lasting visual
artifacts. For example, the brightening or darkening of a sub-pixel
may not result in a lasting artifact if the sub-pixel's data line
is subsequently updated to a target data voltage during the
updating of the sub-pixel's row in the current frame. This
subsequent update can overwrite the changes in voltage that caused
these visual artifacts. In contrast, visual artifacts may persist
in sub-pixels that have already been written with data in the
current frame because the brightening or darkening can remain until
the sub-pixel is updated again in the next frame.
[0005] Various embodiments of the present disclosure serve to
prevent or reduce these persisting visual artifacts by offsetting
their effects or by distributing their presence among different
colored sub-pixels. In some embodiments, this may be accomplished
by using different write sequences during the update of a row of
pixels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A illustrates an example mobile telephone according to
embodiments of the disclosure.
[0007] FIG. 1B illustrates an example digital media player
according to embodiments of the disclosure.
[0008] FIG. 1C illustrates an example personal computer according
to embodiments of the disclosure.
[0009] FIG. 1D illustrates an example display screen according to
embodiments of the disclosure.
[0010] FIG. 2 illustrates an example thin film transistor (TFT)
circuit according to embodiments of the disclosure.
[0011] FIG. 3A illustrates an example one-column inversion scheme
according to embodiments of the disclosure.
[0012] FIG. 3B illustrates an example two-column inversion scheme
according to embodiments of the disclosure.
[0013] FIG. 3C illustrates an example three-column inversion scheme
according to embodiments of the disclosure.
[0014] FIGS. 4A, 4B, and 4C illustrate an example alternating
voltage polarity pattern according to an embodiment of a column
inversion scheme.
[0015] FIG. 5A illustrates an example one-line inversion scheme
according to embodiments of the disclosure.
[0016] FIG. 5B illustrates an example two-line inversion scheme
according to embodiments of the disclosure.
[0017] FIG. 5C illustrates an example three-line inversion scheme
according to embodiments of the disclosure.
[0018] FIGS. 6A, 6B, and 6C illustrate an example constant voltage
polarity pattern in a line inversion scheme according to
embodiments of the disclosure.
[0019] FIG. 7A illustrates an example dot inversion scheme
according to embodiments of the disclosure.
[0020] FIG. 7B illustrates an example two-column multi-dot
inversion scheme according to embodiments of the disclosure.
[0021] FIG. 7C illustrates an example three-column multi-dot
inversion scheme according to embodiments of the disclosure.
[0022] FIGS. 8A, 8B, and 8C illustrate an example voltage polarity
pattern in a two-column inversion scheme according to embodiments
of the disclosure.
[0023] FIGS. 9A, 9B, and 9C illustrate an example voltage polarity
pattern in a two-column inversion scheme using different write
sequences according to embodiments of the disclosure.
[0024] FIGS. 10A, 10B, and 10C illustrate an example voltage
polarity pattern in a three-column inversion scheme using different
write sequences according to embodiments of the disclosure.
[0025] FIG. 11 illustrates an example circuit diagram for applying
voltages to data lines using different write sequences according to
embodiments of the disclosure.
[0026] FIG. 12 is a block diagram of an example computing system
that illustrates one implementation of an example display screen
according to embodiments of the disclosure.
DETAILED DESCRIPTION
[0027] In the following description of exemplary embodiments,
reference is made to the accompanying drawings in which it is shown
by way of illustration, specific embodiments, of the disclosure. It
is to be understood that other embodiments can be used and
structural changes can be made without departing from the scope of
the embodiments of the disclosure.
[0028] Furthermore, although embodiments of the disclosure may be
described and illustrated herein in terms of logic performed within
a display driver, host video driver, etc., it should be understood
that embodiments of the disclosure are not so limited, but can also
be performed within a display subassembly, liquid crystal display
driver chip, or within another module in any combination of
software, firmware, and/or hardware.
[0029] Various embodiments of the invention use different write
sequences to write data to a row of sub-pixels in a display screen
during an update of the sub-pixels' row. These write sequences can
control the sequence in which voltage is applied to each
sub-pixel's data lines. In some scanning operations of display
screens, such as some liquid crystal display inversion schemes, a
large change in voltage on a data line can affect the voltages on
adjacent data lines due to capacitive coupling between data lines.
The resulting change in voltage on these adjacent data lines can
give rise to visual artifacts in the data lines' corresponding
sub-pixels. Using different write sequences can reduce or eliminate
the presence of these visual artifacts.
[0030] FIGS. 1A-1D show example systems in which display screens
(which can be part of touch screens) according to embodiments of
the disclosure may be implemented. FIG. 1A illustrates an example
mobile telephone 136 that includes a display screen 124. FIG. 1B
illustrates an example digital media player 140 that includes a
display screen 126. FIG. 1C illustrates an example personal
computer 144 that includes a display screen 128. FIG. 1D
illustrates an example display screen 150, such as a stand-alone
display. In some embodiments, display screens 124, 126, 128, and
150 can be touch screens in which touch sensing circuitry can be
integrated into the display pixels. Touch sensing can be based on,
for example, self capacitance or mutual capacitance, or another
touch sensing technology. In some embodiments, a touch screen can
be multi-touch, single touch, projection scan, full-imaging
multi-touch, or any capacitive touch.
[0031] In some scanning methods, the direction of the electric
field across the pixel material can be reversed periodically. In
LCD displays, for example, periodically switching the direction of
the electric field can help prevent the molecules of liquid crystal
from becoming stuck in one direction. Switching the electric field
direction can be accomplished by reversing the polarity of the
electrical potential between the pixel electrode and the Vcom. In
other words, a positive potential from the pixel electrode to the
Vcom can generate an electric field across the liquid crystal in
one direction, and a negative potential from the pixel electrode to
the Vcom can generate an electric field across the liquid crystal
in the opposite direction. In some scanning methods, switching the
polarity of the potential between the pixel electrode and the Vcom
can be accomplished by switching the polarities of the voltages
applied to the pixel electrode and the Vcom. For example, during an
update of an image in one frame, a positive voltage can be applied
to the pixel electrode and a negative voltage can be applied to the
Vcom. In a next frame, a negative voltage can be applied to the
pixel electrode and a positive voltage can be applied to the Vcom.
One skilled in the art would understand that switching the polarity
of the potential between the pixel electrode and the Vcom can be
accomplished without switching the polarity of the voltage applied
to either or both of the pixel electrode and Vcom. In this regard,
although example embodiments are described herein as switching the
polarity of voltages applied to data lines, and correspondingly, to
pixel electrodes, it should be understood that reference to
positive/negative voltage polarities can represent relative voltage
values. For example, an application of a negative polarity voltage
to a data line, as described herein, can refer to application of a
voltage with a positive absolute value (e.g., +1V) to the data
line, while a higher voltage is being applied to the Vcom, for
example. In other words, in some cases, a negative polarity
potential can be created between the pixel electrode and the Vcom
by applied positive (absolute value) voltages to both the pixel
electrode and the Vcom, for example.
[0032] FIG. 1D illustrates some details of an example display
screen 150. FIG. 1D includes a magnified view of display screen 150
that shows multiple display pixels 153, each of which can include
multiple display sub-pixels, such as red (R), green (G), and blue
(B) sub-pixels in an RGB display, for example. Data lines 155 can
run vertically through display screen 150, such that a set 156 of
three data lines (an R data line 155a, a G data line 155b, and a B
data line 155c) can pass through an entire column of display pixels
(e.g., vertical line of display pixels).
[0033] FIG. 1D also includes a magnified view of two of the display
pixels 153, which illustrates that each display pixel can include
pixel electrodes 157, each of which can correspond to one of the
sub-pixels, for example. Each display pixel can include a common
electrode (Vcom) 159 that can be used in conjunction with pixel
electrodes 157 to create an electrical potential across a pixel
material (not shown). Varying the electrical potential across the
pixel material can correspondingly vary an amount of light
emanating from the sub-pixel. In some embodiments, for example, the
pixel material can be liquid crystal. A common electrode voltage
can be applied to a Vcom 159 of a display pixel, and a data voltage
can be applied to a pixel electrode 157 of a sub-pixel of the
display pixel through the corresponding data line 155. A voltage
difference between the common electrode voltage applied to Vcom 159
and the data voltage applied to pixel electrode 157 can create the
electrical potential through the liquid crystal of the sub-pixel.
The electrical potential can generate an electric field through the
liquid crystal, which can cause inclination of the liquid crystal
molecules to allow polarized light from a backlight (not shown) to
emanate from the sub-pixel with a luminance that depends on the
strength of the electric field (which can depend on the voltage
difference between the applied common electrode voltage and data
voltage). In other embodiments, the pixel material can include, for
example, a light-emitting material, such as can be used in organic
light emitting diode (OLED) displays.
[0034] In this example embodiment, the three data lines 155 in each
set 156 can be operated sequentially. For example, a display driver
or host video driver (not shown) can multiplex an R data voltage, a
G data voltage, and a B data voltage onto a single data voltage bus
line 158 in a particular sequence, and then a demultiplexer 161 in
the border region of the display can demultiplex the R, G, and B
data voltages to apply the data voltages to data lines 155a, 155b,
and 155c in the particular sequence. Each demultiplexer 161 can
include three switches 163 that can open and close according to the
particular sequence of sub-pixel charging for the display pixel. In
an R-G-B sequence, for example, data voltages can be multiplexed
onto data voltage bus line 158 such that R data voltage is applied
to R data line 155a during a first time period, G data voltage is
applied to G data line 155b during a second time period, and B data
voltage is applied to B data line 155c during a third time period.
Demultiplexer 161 can demultiplex the data voltages in the
particular sequence by closing switch 163 associated with R data
line 155a during the first time period when R data voltage is being
applied to data voltage bus line 158, while keeping the green and
blue switches open such that G data line 155b and B data line 155c
are at a floating potential during the application of the R data
voltage to the R data line. In this way, for example, the red data
voltage can be applied to the pixel electrode of the red sub-pixel
during the first time period. During the second time period, when G
data voltage is being applied to G data line 155b, demultiplexer
161 can open the red switch 163, close the green switch 163, and
keep the blue switch 163 open, thus applying the G data voltage to
the G data line, while the R data line and B data line are
floating. Likewise, the B data voltage can be applied during the
third time period, while the G data line and the R data line are
floating.
[0035] As will be described in more detail below with respect to
example embodiments, applying a data voltage to a data line can
affect the voltages on surrounding, floating data lines. In some
cases, the effect on the voltages of floating data lines can affect
the luminance of the sub-pixels corresponding to the affected data
lines, causing the sub-pixels to appear brighter or darker than
intended. The resulting increase or decrease in sub-pixel luminance
can be detectable as a visual artifact in some displays.
[0036] In some embodiments, thin film transistors (TFTs) can be
used to address display pixels, such as display pixels 153, by
scanning lines of display pixels (e.g., rows of display pixels) in
a particular order. When each line is updated during the scan of
the display, data voltages corresponding to each display pixel in
the updated line can be applied to the set of data lines of the
display pixel through the demuxing procedure described above, for
example.
[0037] FIG. 2 illustrates a portion of an exemplary TFT circuit 200
according to embodiments of the present disclosure. As shown by the
figure, the thin film transistor circuit 200 can include multiple
pixels 202 arranged into rows, or scan lines, with each pixel 202
containing a set of color sub-pixels 204 (red, green, and blue,
respectively). It is understood that a plurality of pixels can be
disposed adjacent each other to form a row of the display. Each
color reproducible by the liquid crystal display can therefore be a
combination of three levels of light emitted from a particular set
of color sub-pixels 204.
[0038] Color sub-pixels may be addressed using the thin film
transistor circuit's 200 array of scan lines (called gate lines
208) and data lines 210. Gate lines 208 and data lines 210 formed
in the horizontal (row) and vertical (column) directions,
respectively, and each column of display pixels can include a set
211 of data lines including an R data line, a G data line, and a B
data line. Each sub-pixel may include a pixel TFT 212 provided at
the respective intersection of one of the gate lines 208 and one of
the data lines 210. A row of sub-pixels may be addressed by
applying a gate signal on the row's gate line 208 (to turn on the
pixel TFTs of the row), and by applying voltages on the data lines
210 corresponding to the amount of emitted light desired for each
sub-pixel in the row. The voltage level of each data line 210 may
be stored in a storage capacitor 216 in each sub-pixel to maintain
the desired voltage level across the two electrodes associated with
the liquid crystal capacitor 206 relative to a voltage source 214
(denoted here as V.sub.cf). A voltage V.sub.cf may be applied to
the counter electrode (common electrode) forming one plate of the
liquid crystal capacitance with the other plate formed by a pixel
electrode associated with each sub-pixel. One plate of each of the
storage capacitors 216 may be connected to a common voltage source
Cst along line 218.
[0039] Applying a voltage to a sub-pixel's data line can charge the
sub-pixel (e.g., the pixel electrode of the sub-pixel) to the
voltage level of the applied voltage. Demultiplexer 220 in the
border region of the display can be used to apply the data voltages
to the desired data line. For example, demultiplexer 220 can apply
data voltages to the R data line, the G data line, and the B data
line in a set 211 in a particular sequence, as described above with
reference to FIG. 1D. Therefore, while a voltage can be applied to
one data line (e.g., red), the other data lines (e.g., green and
blue) in the pixel can be floating. However, applying a voltage to
one data line can affect the voltage on floating data lines, for
example, because a capacitance existing between data lines can
allow voltage changes on one data line to be coupled to other data
lines. This capacitive coupling can change the voltage on the
floating data lines, which can make the sub-pixels corresponding to
the floating data lines appear either brighter or darker depending
on whether the voltage change on the charging data line is in the
same direction or opposite direction, respectively, as the polarity
of the floating data line voltage. In addition, the amount of
voltage change on the floating data line can depend on the amount
of the voltage change on the charging data line.
[0040] By way of example, a negative data voltage, e.g., -2V, may
be applied to data line A during the scan of a first line. Then,
during the scan of the next line, a positive data voltage, e.g.,
+2V, may be applied to data line A, thus swinging the voltage on
data line A from -2V to +2V, i.e., a positive voltage change of
+4V. Voltages on floating data lines surrounding data line A can be
increased by this positive voltage swing. For example, the positive
swing on data line A can increase the voltage of an adjacent data
line B floating at a positive voltage, thus, increasing the
magnitude of the positive floating voltage and making the sub-pixel
corresponding to data line B appear brighter. Likewise, the
positive voltage swing on data line A can increase the voltage of
an adjacent data line C floating at a negative voltage, thus
decreasing the magnitude of the negative floating voltage and
making the sub-pixel corresponding to sub-pixel C appear darker.
Thus, the appearance of visual artifacts of brighter or darker
sub-pixels can depend on, for example, the occurrence of large
voltage changes on one or more data lines during scanning of a
display and the polarity of surrounding data lines with floating
voltages during the large voltage changes.
[0041] In addition, the appearance of visual artifacts can depend
on the particular sequence in which the data voltages are applied.
Further to the example above, after a data voltage is applied to
data line A, a data voltage may be applied to data line B (data
line B being next in sequence). In this case, the effect of the
voltage swing on data line A, i.e., the increase in the voltage on
data line B, can be "overwritten" by the subsequent charging of
data line B.
[0042] While the particular sequence in which the data voltages are
applied to a set of data lines can be independent of the type of
inversion scheme, the occurrence of large voltage changes in data
lines, and the polarities of the floating voltages on adjacent data
lines during the large voltage changes, can each depend on the type
of inversion scheme used to operated the display. In some displays,
a column inversion scheme, a line (row) inversion scheme, or a dot
inversion scheme can be used, for example. Some example inversion
schemes, and corresponding mechanisms that can introduce the
display artifacts described above, will now be described.
[0043] Column Inversion
[0044] In a column inversion scheme, for example, the polarity of
the data voltages applied to a particular data line can remain the
same throughout the scan of all of the rows of the display in one
frame update, i.e., an update of the displayed image by scanning
through all of the rows to update the voltages on each sub-pixel of
the display. In other words, while the particular voltage values
applied to a particular data line can change from one row scan to
another row scan, the polarity of the data voltages on the
particular data line can remain the same throughout the scan. In
the next frame, the polarity of the data voltages can be reversed,
for example. In other words, polarity changes on data line voltage
may only occur in between frames. Therefore, large voltage changes
(e.g., a swing in voltage from one polarity to another polarity) on
a data line may only occur during the scan of the first line of a
new frame, for example.
[0045] While the polarity of the data line voltages applied to each
data line can remain the same throughout the scan of a single frame
in column inversion, the polarity of the voltage applied to each
data line can alternate across a scanned row of sub-pixels; i.e.,
during a scan of one row, positive polarity data voltages can be
applied to some of the data lines and negative polarity data
voltages can be applied to the other data lines.
[0046] This alternating pattern is illustrated in FIG. 3A which
shows columns with voltages of alternating polarities. The polarity
of the voltage can remain the same along a column but alternate
across a row. In the next frame, the polarity of the data voltages
can be reversed. Other column inversion schemes, including
two-column inversion illustrated in FIG. 3B, and three-column
inversion illustrated in FIG. 3C, can operate according to similar
principles.
[0047] FIGS. 4A, 4B, and 4C illustrate an example alternating
voltage polarity pattern across a scanned row in one embodiment of
a column inversion scheme. FIGS. 4A, 4B, and 4C illustrate two
adjacent pixels 402 and 404 along the same row at different points
in time, T0, T1, and T2, during a scan of the row. Pixel 402 has a
red sub-pixel with red data line 406, a green sub-pixel with green
data line 408, and a blue sub-pixel with blue data line 410. A
demultiplexer 418 located in the border region of the display can
operate the data lines of pixel 402. The demultiplexer receives the
RGB data signals for each sub-pixel and feeds each signal to the
appropriate RGB data line at the appropriate timing as dictated by
timing and control circuitry (not shown), for example, as described
above. Pixel 404 similarly has a red data line 412, a green data
line 414, a blue data line 416, and a demultiplexer 420. Although
writing, i.e., application of data voltages to the data lines, may
occur in any sequence, the embodiment shown in FIGS. 4A, 4B, and 4C
uses an RGB write sequence for each sub-pixel.
[0048] An RGB write sequence for the sub-pixels may be applied
simultaneously to each sub-pixel in a row of the display during the
scan of the row. After the scan of the row is complete, a next row
in the scanning order can be likewise scanned. The scanning process
can continue scanning rows in a particular scanning order until all
of the rows of the display are refreshed, i.e., a single frame
update.
[0049] The RGB write sequence first writes data to each red
sub-pixel in the row at time T0; next writes data to each green
sub-pixel in the row at time T1; and finally writes data to each
blue sub-pixel in the row at time T2. To accomplish this writing
sequence, demultiplexers select the desired sub-pixel for writing,
while a voltage can then be applied to the sub-pixel's
corresponding data line. As shown in FIGS. 4A, 4B, and 4C, a "+" or
"-" is located above each sub-pixel data line. These signs
represent the polarity of the sub-pixel's data line voltage from
the previous update. The "+" or "-" sign next to the closed switch
represents the polarity of the voltage being applied to the data
line. In the present example, pixels 402 and 404 may be in the
first row scanned in a frame. In this example, the polarity of the
data voltages can be reversed in between the previous frame and the
new frame. Therefore, the "+" or "-" sign above each sub-pixel data
line shows the prior voltage polarity from the previous update.
This polarity is opposite to the polarity of the voltage applied in
the current update. In this case, the data line voltages applied in
the scan of this first row can result in a large voltage change in
each data line, as the voltage on each data line can swing from +
to - or from - to +.
[0050] FIG. 4A, for example, illustrates the writing of data to the
red sub-pixels by application of a voltage to red data lines 406
and 412 at time T0. As illustrated, demultiplexers 418 and 420 can
apply a voltage to the red data lines. Doing so can change the
polarity of the voltages on red data line 406 from + to - and from
- to + on red data line 412. Because the voltages applied to the
red data lines can swing the data line voltages from one polarity
to the opposite polarity, the voltage change on the red data lines
can be large. While a voltage is being applied to the red data
lines, the green and blue data lines can be floating. The large
voltage change on the red data lines can affect the voltages on
other data lines, for example, due to capacitive coupling between
data lines. In particular, the capacitance existing between two
data lines can allow voltage changes on one data line to affect the
voltages on other data lines. While there may be some amount of
capacitance existing between a particular data line and each and
every other data line, the amount of capacitance can vary depending
on the distance between two data lines and may be greatest between
two adjacent data lines. Accordingly, the following discussion can
ignore the impact on non-adjacent data lines.
[0051] Here, the voltage on red data line 406 can swing from a
positive polarity to a negative polarity. The negative change in
voltage can affect the negative voltage on green data line 408.
Because the voltage on green data line 408 is negative, the
negative change in voltage on red data line 406 can increase the
magnitude of the negative voltage on green data line 408.
Accordingly, the sub-pixel corresponding to green data line 408 can
brighten. This brightening effect is represented by the upward
pointing arrow above green data line 408. Although the negative
change in voltage can also affect the voltage on blue data line
410, the blue data line is not adjacent to the red data line. As
such, the impact on blue data line 410 can be ignored.
[0052] With respect to red data line 412, the swing in voltage from
a negative polarity to a positive polarity can affect the voltage
on green data line 414. Because the voltage on green data line 414
has a positive polarity, the positive change in voltage on red data
line 412 can increase the magnitude of the voltage on green data
line 414, which can cause the corresponding green sub-pixel to
brighten. This brightening effect is represented by the upward
pointing arrow above green data line 414. Similarly, the positive
change in voltage on red data line 412 can increase the magnitude
of the positive voltage on blue data line 410 in adjacent pixel
402, which can cause the corresponding blue sub-pixel to appear
brighter. The impact on non-adjacent blue data line 416 can be
ignored.
[0053] FIG. 4B illustrates the writing of data to the green
sub-pixels by application of a voltage to green data lines 408 and
414 at time T1. As illustrated, demultiplexers 418 and 420 can
apply a voltage to the green data lines. Doing so can change the
polarity of the voltage on green data line 408 from - to + and the
polarity of the voltage on green data line 414 from + to -. The
application of voltages to green data lines 408 and 414 can
overwrite any changes in voltage that occurred on the green data
lines before time T1. This overwriting is represented by the
absence of the upward pointing arrows above green data lines 408
and 414.
[0054] The large voltage change on the green data lines can affect
the voltages on the red and blue data lines. In this example, the
large positive voltage change on green data line 408 can swing the
polarity from - to +. This large positive voltage change can cause
a positive voltage change in red data line 406. Because the
polarity of red data line 406 voltage is negative, the positive
voltage change on green data line 408 can reduce the magnitude of
the red data line 406 voltage, which can make the corresponding red
sub-pixel to appear darker. This darkening effect is represented by
the downward pointing arrow above red data line 406. The large
positive voltage change on green data line 408 can increase the
magnitude of the positive voltage on blue data line 410, which can
cause the corresponding blue sub-pixel to appear brighter. This
brightening effect is represented by the upward pointing arrow
above blue data line 410. As illustrated in FIG. 4B, two upward
pointing arrows appear above blue data line 410 because the
corresponding blue sub-pixel can brighten first at time T0 and
again at time T1.
[0055] The change in voltage on green data line 414 can affect the
voltage on red data line 412 and blue data line 416. With respect
to red data line 412, the large negative change in voltage on green
data line 414 can decrease the magnitude of the positive voltage on
red data line 412, which can make the corresponding red sub-pixel
appear darker as represented by the downward pointing arrow. With
respect to blue data line 416, the large negative change in voltage
on green data line 414 can increase the magnitude of the negative
voltage on blue data line 416, which can make corresponding blue
sub-pixel appear brighter as represented by the upward pointing
arrow.
[0056] FIG. 4C illustrates the writing of data to the blue
sub-pixels by application of a voltage to blue data lines 410 and
416. Just as above, demultiplexers 418 and 420 apply a voltage to
the blue data lines. Doing so changes the polarity of the voltages
on the blue data lines from + to - on data line 410 and from - to +
on data line 416. The application of voltages to blue data lines
410 and 416 can overwrite any changes in voltage that occurred on
the blue data lines before time T2. This overwriting is represented
by the absence of the upward pointing arrows above blue data lines
410 and 416.
[0057] The change in voltage on blue data line 410 can affect the
voltage on green data line 408 and red data line 412 in adjacent
pixel 404. Although the change in voltage on blue data line 410 can
also affect the voltage on non-adjacent red data line 406, this
impact can be ignored. With respect to green data line 408, the
large negative change in voltage on blue data line 410 can cause a
negative voltage change on green data line 408. Because the
polarity of green data line 408 is positive, the negative voltage
change can reduce the magnitude of the green data line voltage,
which can make the green sub-pixel appear darker as represented by
the downward pointing arrow. With respect to red data line 412, the
large negative voltage change on blue data line 410 can reduce the
magnitude of the positive voltage on red data line 412 in the
adjacent pixel, which can make the red sub-pixel appear darker as
represented by the downward pointing arrow. As illustrated in FIG.
4C, two downward pointing arrows appear above red data line 412
because the corresponding red sub-pixel can darken first at time T1
and again at time T2.
[0058] In a similar fashion, the large positive change in voltage
on blue data line 416 can change the voltage on green data line
414. This positive voltage change can reduce the magnitude of the
negative voltage on green data line 414, which can make the green
sub-pixel appear darker as represented by the downward pointing
arrow. The impact on non-adjacent red data line 412 can be
ignored.
[0059] As illustrated by the downward pointing arrows above red
data lines 406 and 412 and green data lines 408 and 414 in FIG. 4C,
visual artifacts can appear in the data lines' corresponding
sub-pixels when the illustrated column inversion scheme is
used.
[0060] Line (Row) Inversion
[0061] In line (row) inversion, the polarity of the voltages
applied to the data lines during the scan of one row can be
different from the polarity of the voltages applied during the scan
of another row in the same frame. In contrast to column inversion,
large changes in data voltages can occur for multiple scan lines
due to multiple changes in polarity throughout the scanning of a
single frame. Capacitive coupling between data lines can also
introduce visual artifacts in line inversion schemes.
[0062] In line inversion, the polarity of the voltage on each
sub-pixel is the same for all sub-pixels in the same row, and this
polarity alternates from row to row. This configuration is
illustrated in FIG. 5A. In the next frame, the polarity of the data
voltages can be reversed. Other line inversion schemes, including
two-line inversion illustrated in FIG. 5B, and three-line inversion
illustrated in FIG. 5C, can operate according to similar
principles. In two-line inversion, every block of two rows can have
the same polarity. In three-line inversion, every block of three
rows can have the same polarity.
[0063] FIGS. 6A, 6B, and 6C illustrate an example of a constant
voltage polarity pattern across a scanned row in one embodiment of
a line inversion scheme. FIGS. 6A, 6B, and 6C illustrate two
adjacent pixels 602 and 604 arranged along the same row at
different points in time, T0, T1, and T2, during a scan of the row.
Pixel 602 has a red sub-pixel with red data line 606, a green
sub-pixel with green data line 608, a blue sub-pixel with blue data
line 610. A demultiplexer 618 located in the border region of the
display can operate the data lines of pixel 602. The demultiplexer
receives the RGB data signals for each sub-pixel and feeds each
signal to the appropriate RGB data line at the appropriate timing
as dictated by timing and control circuitry (not shown), for
example, as described above. Pixel 604 similarly has a red data
line 612, a green data line 614, a blue data line 616, and a
demultiplexer 604. Although writing, i.e., application of data
voltages to the sub-pixels, may occur in any sequence, the
embodiment shown in FIGS. 6A, 6B, and 6C uses an RGB write sequence
for each sub-pixel.
[0064] As explained above, an RGB write sequence for the sub-pixels
may be applied simultaneously to each sub-pixel in a row of the
display during the scan of the row. After the scan of the row is
complete, a next row in the scanning order can be likewise scanned
until all of the rows of the display are refreshed, i.e., a single
frame update.
[0065] The RGB write sequence first writes data to each red
sub-pixel in the row at time T0; next writes data to each green
sub-pixel in the row at time T1; and finally writes data to each
blue sub-pixel in the row at time T2. To accomplish this writing
sequence, demultiplexers select the desired sub-pixel for writing,
while a voltage is then applied to the sub-pixel's corresponding
data line. As shown in FIGS. 6A, 6B, and 6C, a "+" or "-" is
located above each data line. Like FIGS. 4A, 4B, and 4C, these
signs represent the polarity of the sub-pixel's data line voltage
value from the previous update. The "+" or "-" sign next to the
closed switch represents the polarity of the voltage being applied
to the data line. In the present example, pixels 602 and 604 may be
in the first row scanned in a frame. In this example, the polarity
of the data line voltages can be reversed in between the previous
frame and the new frame. In this case, the data line voltages
applied in the scan of this first row can result in a large voltage
change in each data line, as the voltage on each data line can
swing from + to - or from - to +.
[0066] FIG. 6A, for example, illustrates the writing of data to the
red sub-pixels by application of a voltage to red data lines 606
and 612 at time T0. As illustrated, demultiplexers 618 and 620 can
apply a voltage to red data lines 606 and 612. Doing so can change
the polarity of the voltages on red data lines 606 and 612 from -
to +. Because the voltages applied to the red data lines can swing
the data line voltages from one polarity to the opposite polarity,
the voltage change on the red data lines can be large during the
scan of the first row in each update block. While these voltages
are applied to the red data lines, the green and blue data lines
can be floating.
[0067] As such, the large voltage changes on the red data lines can
affect the voltages on adjacent data lines.
[0068] With respect to red data line 606, the large positive change
in voltage can reduce the magnitude of the negative voltage on
green data line 608, which can cause the corresponding green
sub-pixel to appear darker. This darkening effect is represented by
the downward pointing arrow above green data line 608. The impact
on non-adjacent blue data line 610 due to the change in voltage on
red data line 606 can be ignored.
[0069] With respect to red data line 612, the large positive change
in voltage can reduce the magnitude of the negative voltages on
green data line 614 and blue data line 610 in adjacent pixel 602.
The reduction in voltage magnitude can cause the corresponding
green and blue sub-pixels to appear darker. This darkening effect
is represented by the downward pointing arrows above green data
line 614 and blue data line 610. The impact on non-adjacent blue
data line 616 due to the change in voltage on red data line 612 can
be ignored.
[0070] FIG. 6B illustrates the writing of data to the green
sub-pixels by application of a voltage to green data lines 608 and
614 at time T1. As illustrated, demultiplexers 618 and 620 apply a
voltage to the green data lines. Doing so can change the polarity
of the voltages on the green data lines 608 and 614 from - to +.
The application of voltages to green data lines 608 and 614 can
overwrite any changes in voltage that occurred on the green data
lines before time T1. This overwriting is represented by the
absence of the upward pointing arrows above green data lines 608
and 614.
[0071] The large voltage change on the green data lines can affect
the voltages on the red data lines, for example, due to capacitive
coupling between data lines. In this example, the large positive
voltage change on the green data lines 608 and 614 can swing the
polarity from - to +. This positive voltage difference can cause a
positive voltage change on red data lines 606 and 612. Because the
polarity of the red data line voltage is positive, the positive
voltage change can increase the magnitude of the red data line
voltages, which can make the red sub-pixels appear brighter as
represented by the upward pointing arrows above red data lines 606
and 612.
[0072] The change in voltage on the green data lines can also
affect the voltage level of blue sub-pixels corresponding to data
lines 610 and 616. In this example, the large positive voltage
change on the green data lines 608 and 614 can reduce the magnitude
of the negative voltages on blue data lines 610 and 616, which can
make the corresponding blue sub-pixels appear darker. This
darkening effect is represented by the downward pointing arrows
above blue data lines 610 and 616.
[0073] Two downward pointing arrows appear above blue data line 610
because the corresponding blue sub-pixel can first darken at time
T0 and again at time T1.
[0074] FIG. 6C illustrates the writing of data to the blue
sub-pixels by application of a voltage to blue data lines 610 and
616. Just as above, demultiplexers 618 and 620 can apply a voltage
to the blue data lines. Doing so changes the polarity of the
voltages on blue data lines 610 and 616 from - to +. The
application of voltages to blue data lines 610 and 616 can
overwrite any changes in voltage that occurred on the blue data
lines before time T2. This overwriting is represented by the
absence of the downward pointing arrows above blue data lines 610
and 616.
[0075] The large positive change in voltage on blue data line 610
can affect the voltage on blue data line 608. In this example, the
positive change in voltage on blue data line 610 can increase the
magnitude of the positive voltage on green data line 608, which can
cause the corresponding green sub-pixel to appear brighter.
Similarly, the positive change in voltage on blue data line 610 can
increase the magnitude of the positive voltage on red data line 612
in adjacent pixel 604, which can cause the corresponding red
sub-pixel to brighten. These brightening effects are represented by
the upward pointing arrows above green data line 608 and red data
line 612. Two upward pointing arrows appear above red data line 612
because the corresponding red sub-pixel can brighten first at time
T1 and again_at time T2. The impact on non-adjacent red data line
606 due to the change in voltage on blue data line 610 can be
ignored.
[0076] The large positive change in voltage on blue data line 616
can similarly increase the magnitude of the positive voltage on
green data line 614, which can cause the corresponding green
sub-pixel to appear brighter as represented by the upward pointing
arrow above green data line 614. The impact on non-adjacent red
data line 612 due to the change in voltage on blue data line 616
can be ignored.
[0077] As illustrated by the upward pointing arrows above red data
lines 606 and 612 and green data lines 608 and 614 in FIG. 4C,
visual artifacts can appear in the data lines' corresponding
sub-pixels when the illustrated line inversion scheme is used.
[0078] Dot Inversion
[0079] A dot inversion scheme combines both line inversion and
column inversion. Accordingly, the polarity of the data voltages
applied to the data lines can be inverted along every data line as
well as every row. In the next frame, the polarity of the data
voltage can be reversed. This configuration is illustrated in FIG.
7A which shows, for example, alternating rows and columns of + and
- voltages. In the next frame, the polarity of the data voltages
can be reversed. Other dot inversion schemes, including two-column
multi-dot inversion illustrated in FIG. 7B, and three-column
multi-dot inversion illustrated in FIG. 7C, can operate according
to similar principles.
[0080] With respect to each row of the display panel, the dot
inversion schemes illustrated in FIGS. 7A, 7B, and 7C can resemble
column inversion schemes. In the first row of the dot inversion
scheme illustrated in FIG. 7A, for example, there are alternating
columns of + and - voltages. This configuration is similar to using
a one-column inversion scheme along the row. Similar patterns may
apply to FIGS. 7B and 7C. In the first row of the two-column
multi-dot inversion scheme illustrated in FIG. 7B, for example,
alternating groups of two columns each have + and - voltages. This
configuration is similar to using a two-column inversion scheme
along each row.
[0081] Similarly, each row of a three-column multi-dot inversion
scheme may resemble a three-column inversion scheme.
[0082] In view of the similarity between dot inversion and column
inversion, similar visual artifacts described above with respect to
column inversion can also apply to each row of a dot inversion
scheme.
[0083] As explained above with respect to the different inversion
schemes, a large change in voltage on a data line can affect the
voltages on adjacent data lines due to capacitive coupling between
data lines. The resulting change in voltage on these adjacent data
lines can give rise to visual artifacts in the data lines'
corresponding sub-pixels. However, not all sub-pixels will have
lasting visual artifacts. For example, the brightening or darkening
of a sub-pixel may not result in a lasting artifact if the
sub-pixel's data line is subsequently updated to a target data
voltage during the updating of the sub-pixel's row in the current
frame. This subsequent update can overwrite the changes in voltage
that caused these visual artifacts. In contrast, visual artifacts
may persist in sub-pixels that have already been written with data
in the current frame because the brightening or darkening can
remain until the sub-pixel is updated again in the next frame.
Various embodiments of the present disclosure serve to prevent or
reduce these persisting visual artifacts by offsetting their
effects or by distributing their presence among different colored
sub-pixels. In some embodiments, this may be accomplished by using
different write sequences during the update of a row of pixels.
[0084] By way of example, a method of offsetting the appearance of
visual artifacts may be described with respect to an embodiment of
a two-column inversion scheme. The following description first
describes how visual artifacts appear in a two-column inversion
scheme. This description is followed by an explanation of how these
visual artifacts may be offset.
[0085] As illustrated in FIG. 3B, in a two-column inversion scheme,
groups of two adjacent columns have the same polarity. This
polarity alternates from group to group. FIGS. 8A, 8B, and 8C
illustrate an example alternating voltage polarity pattern across a
scanned row in one embodiment of a two-column inversion scheme.
FIGS. 8A, 8B, and 8C illustrate an example embodiment in which a
particular selection of write sequence can be combined with a
particular selection of inversion scheme such that an offsetting
brightening and darkening can be made to occur in each of one or
more sub-pixels. In other words, some of the-sub-pixels can be
affected by both a brightening and a darkening during the scanning
of a line. In this way, for example, the effect of the brightening
can be offset by the effect of the darkening (or vice versa) within
the same sub-pixel. This effect can be referred to herein as a
single sub-pixel offsetting, which can reduce or eliminate the
appearance of a visual artifact in the sub-pixel. FIGS. 8A, 8B, and
8C also illustrate that a particular write sequence and inversion
scheme combination can allow for multiple sub-pixel offsetting, in
which sub-pixels of the same color are brightened in one pixel and
darkened in an adjacent pixel. In this way, for example, the
appearance of a visual artifact can be reduced or eliminated due to
opposing errors in brightness being made to occur in sub-pixels in
adjacent pixels.
[0086] FIGS. 8A, 8B, and 8C illustrate three adjacent pixels 800,
810, and 820 along the same row at different points in time, T0,
T1, and T2, during a scan of the row. Pixel 800 has a red sub-pixel
with red data line 802, a green sub-pixel with green data line 804,
and a blue sub-pixel with blue data line 806. Above each
sub-pixel's data line is a "+" or "-" sign. These signs show the
prior voltage polarity on the data line from the previous update.
The "+" or "-" sign next to the closed switch represents the
polarity of the voltage being applied to the data line. A
demultiplexer 808 located in the border region of the display can
receive the RGB data signals for each sub-pixel and feed each
signal to the appropriate RGB data line at the appropriate timing
as dictated by timing and control circuitry (not shown), for
example, as described above. Pixels 810 and 820 have a similar
structure as pixel 810. The embodiment shown in FIGS. 8A, 8B, and
8C uses an RGB write sequence for each sub-pixel.
[0087] FIG. 8A, for example, illustrates the writing of data to the
red sub-pixels by application of a voltage to red data lines 802,
812, and 822 at time T0. As illustrated, demultiplexers 808, 818,
and 828 can apply a voltage to the red data lines. Doing so can
change the polarity of the voltage on red data line 802 from + to
-, the polarity of the voltage on red data line 812 from + to -,
and the polarity of the voltage on red data line 822 from - to +.
While a voltage is being applied to the red data lines, the green
and blue data lines are floating. Accordingly, the large voltage
changes on the red data lines can affect the voltages on the
floating data lines as described below.
[0088] With respect to red data line 802, the negative change in
voltage can increase the magnitude of the negative voltage on green
data line 804, which can cause the corresponding green sub-pixel to
appear brighter. This brightening effect is represented by the
upward pointing arrow above green data line 804. The impact on
non-adjacent blue data line 806 can be ignored.
[0089] With respect to red data line 812, the negative change in
voltage on the red data line can affect the voltage on green data
line 814 and blue data line 806 in adjacent pixel 800. The negative
change in voltage on red data line 812 can decrease the magnitude
of the positive voltage on green data line 814, which can cause the
corresponding green sub-pixel to appear darker as represented by
the downward pointing arrow above green data line 814. The negative
change in voltage on red data line 812 can increase the magnitude
of the negative voltage on blue data line 806, which can cause the
corresponding blue sub-pixel to appear brighter as represented by
the upward pointing arrow above blue data line 806.
[0090] With respect to red data line 822, the positive change in
voltage on the red data line can affect the voltage on green data
line 824 and blue data line 816 in adjacent pixel 810. The positive
change in voltage on red data line 822 can increase the magnitude
of the positive voltage on green data line 824, which can cause the
corresponding green sub-pixel to appear brighter as represented by
the upward pointing arrow above green data line 824. The positive
change in voltage on red data line 822 can reduce the magnitude of
the negative voltage on blue data line 816, which can cause the
corresponding blue sub-pixel to appear darker as represented by the
downward pointing arrow above blue data line 816.
[0091] FIG. 8B illustrates the writing of data to the green
sub-pixels by application of a voltage to green data lines 804,
814, and 824 at time T1. Doing so can change the polarity of the
voltage on green data line 804 from - to +, the polarity of the
voltage on green data line 814 from + to -, and the polarity of the
voltage on green data line 824 from + to -. The application of
voltages to green data lines 804, 814, and 824 can overwrite any
changes in voltage that occurred on the green data lines before
time T1. This overwriting is represented by the absence of the
arrows above green data lines 804, 814, and 824.
[0092] The large changes in voltage on the green data lines can
affect the voltages on the red and blue data lines, for example,
due to capacitive coupling between data lines. In this example, the
large positive voltage change on green data line 804 can swing the
voltage polarity from - to +. This positive voltage change can
cause a positive voltage change in red data line 802. Because the
polarity of the voltage on red data line 802 is negative, the
positive voltage change on green data line 804 can reduce the
magnitude of the voltage on red data line 802, which can make the
corresponding red sub-pixel appear darker as represented by the
downward pointing arrow above red data line 802. In a similar
fashion, the large positive change in voltage on green data line
804 can reduce the magnitude of the negative voltage on blue data
line 806, which can make the corresponding blue sub-pixel appear
darker as represented by the downward pointing arrow above blue
data line 806. Blue data line 806 also has an upward pointing arrow
because the corresponding blue sub-pixel can brighten at time
T0.
[0093] Likewise, the large change in voltage on green data line 814
can change the voltage on red data line 812 and blue data line 816.
In this example, the large negative change in voltage on green data
line 814 can increase the magnitude of the negative voltages on red
data line 812 and blue data line 816, which can make the
corresponding red and blue sub-pixels appear brighter as
represented by the upward pointing arrows above red data line 812
and blue data line 816. Blue data line 816 also has a downward
pointing arrow because the corresponding blue sub-pixel can darken
at time T0.
[0094] In a similar manner, the large negative change in voltage on
green data line 824 can decrease the magnitude of the positive
voltages on red data line 822 and blue data line 826, which can
cause the corresponding red and blue sub-pixels to appear darker as
represented by the downward pointing arrows above red data line 822
and blue data line 826.
[0095] FIG. 8C illustrates the writing of data to the blue
sub-pixels by application of a voltage to blue data lines 806, 816,
and 826. Doing so can change the polarity of the voltages on the
blue data lines from - to + on data line 806, from - to + on data
line 816, and from + to - on data line 826. The application of
voltages to blue data lines 806, 816, and 826 can overwrite any
changes in voltage that occurred on the blue data lines before time
T2. This overwriting is represented by the absence of the arrows
above blue data lines 806, 816, and 826.
[0096] With respect to blue data line 806, the large positive
change in voltage can affect the voltage on green data line 804 and
red data line 812 in adjacent pixel 810. This positive change in
voltage can increase the magnitude of the positive voltage on green
data line 804, which can cause the corresponding green sub-pixel to
appear brighter as represented by the upward pointing arrow above
green data line 804. As for red data line 812, the positive change
in voltage on blue data line 806 can reduce the magnitude of the
negative voltage on the red data line, which can make the
corresponding red sub-pixel appear darker as represented by the
downward pointing arrow above red data line 812. An upward pointing
arrow also appears above red data line 812 because the
corresponding red sub-pixel can brighten at time T1.
[0097] In a similar fashion, the large positive change in voltage
on blue data line 816 can affect the voltage on green data line 814
and red data line 822 in adjacent pixel 820. With respect to green
data line 814, the positive change in voltage on blue data line 816
can decrease the magnitude of the negative voltage on green data
line 814, which can make the green sub-pixel appear darker as
represented by the downward pointing arrow above green data line
814. The large positive change in voltage on blue data line 816 can
also cause the sub-pixel corresponding to red data line 822 to
appear brighter as represented by the upward pointing arrow above
red data line 822. A downward pointing arrow also appears above red
data line 822 because the corresponding red sub-pixel can darken at
time T1.
[0098] With respect to blue data line 826, the large negative
change in voltage can increase the magnitude of the negative
voltage on green data line 824, which can make the corresponding
green sub-pixel appear brighter. This brightening effect is
represented by the upward pointing arrow above green data line
824.
[0099] In this embodiment, FIG. 8C represents the end of the scan
of the row. As such, any errors in luminance on the sub-pixel can
persist until the next frame.
[0100] These errors are represented by the arrows above the data
lines. However, not all of these errors will be detectable. As seen
in this example embodiment, the particular combination of the RGB
write sequence with the two-column inversion scheme can allow
offsetting of brightening and darkening to occur, such that some
visual artifacts may not persist long enough to be perceptible.
[0101] Offsetting can occur in two forms, single sub-pixel
offsetting and multiple sub-pixel offsetting. Single sub-pixel
offsetting can occur when a sub-pixel brightens and then darkens
during the scan of the line. Single sub-pixel offsetting can also
apply when a sub-pixel darkens and then brightens during the scan
of the line. The brightening and darkening effects in the sub-pixel
can offset each other. As a consequence of this offset, the change
in luminance on the sub-pixel may not be detectable.
[0102] In contrast, multiple sub-pixel offsetting can occur when
one sub-pixel (e.g., green sub-pixel in pixel 810) brightens and a
like colored sub-pixel in an adjacent pixel (e.g., green sub-pixel
in pixel 820) darkens. Because data is written to the sub-pixels in
a write sequence in a rapid manner, the brightening and darkening
of like colored sub-pixels can offset each other and render the
change in luminance undetectable.
[0103] FIG. 8C illustrates an example of single sub-pixel
offsetting in the sub-pixels corresponding to red data lines 802,
812, and 822. These effects will be first described with respect to
red data lines 812 and 822.
[0104] Single sub-pixel offsetting can occur when a sub-pixel
brightens and darkens. As illustrated in FIG. 8C, the sub-pixel
corresponding to red data line 812 can both brighten and darken as
represented by the upward and downward pointing arrows above red
data line 812. The brightening effect can occur when the voltage on
green data line 814 changes at time T1. The darkening effect can
occur when the voltage on blue data line 806 changes at time T2.
The brightening and darkening of the red sub-pixel can offset each
other and render any errors in luminance undetectable.
[0105] In a similar fashion, the visual artifacts on the sub-pixel
corresponding to red data line 822 may not be perceptible. As
illustrated by the upward and downward pointing arrows above red
data line 822 in FIG. 8C, the sub-pixel corresponding to red data
line 822 can both brighten and darken. The darkening effect can
occur when the voltage on green data line 824 changes at time T1.
The brightening effect can occur when the voltage on blue data line
816 changes at time T2. These brightening and darkening effects can
offset each other.
[0106] Single sub-pixel offsetting can also apply to the sub-pixel
corresponding to red data line 802. Although only a single downward
pointing arrow appears above red data line 802, a person of
ordinary skill in the art would recognize that a change in voltage
on a blue data line (not shown) to the left of red data line 802
can cause the corresponding red sub-pixel to brighten at time T2.
Accordingly, the darkening and brightening of the red sub-pixel can
offset each other.
[0107] FIG. 8C also illustrates an example of multiple sub-pixel
offsetting in the sub-pixels corresponding to green data lines 804,
814, and 824. Multiple sub-pixel offsetting can occur when like
colored sub-pixels in adjacent pixels brighten and darken. As
illustrated by the upward and downward pointing arrows in FIG. 8C,
the sub-pixel corresponding to green data line 814 can darken as
the sub-pixel corresponding to green data line 824 can brighten.
The darkening and brightening of the green colored sub-pixels can
offset each other and render the errors in luminance undetectable.
In a similar fashion, the sub-pixel corresponding to green data
line 804 can brighten and, as one of ordinary skill in the art
would recognize, a green sub-pixel in an adjacent pixel to the left
of green data line 804 can darken.
[0108] FIGS. 9A, 9B, and 9C illustrate an example embodiment in
which two different write sequences, GBR and GRB, can be used
during a scan of the row. As described above, charging a sub-pixel
can require a large change in voltage on the sub-pixel's data line.
This large change in voltage can affect the voltage on adjacent
floating data lines, which can create visual artifacts on these
floating data lines. In this example, using GBR and GRB write
sequences in a two-column inversion scheme can reduce the presence
of these visual artifacts because single sub-pixel offsetting can
occur.
[0109] This example embodiment will be described with respect to
the two-column inversion scheme and write sequence illustrated in
FIGS. 9A, 9B, and 9C. These figures illustrate four adjacent pixels
900, 910, 920, and 930 along the same row at different points in
time, T0, T1, and T2, during a scan of the row. Pixel 900 has a red
sub-pixel with a red data line 902, a green sub-pixel with a green
data line 904, and a blue sub-pixel with a blue data line 906. A
demultiplexer 908 located in the border region of the display can
operate the data lines of pixel 900. Pixels 910, 920, and 930 have
a similar structure as pixel 900.
[0110] As illustrated in FIG. 9A, a voltage can be applied to green
data lines 904, 914, 924, and 934 at time T0. With respect to green
data line 904, for example, the application of a negative voltage
can swing the voltage polarity from positive to negative. This
large negative change in voltage can affect the voltage on red data
line 902 and blue data line 906. With respect to red data line 902,
the large negative change in voltage on green data line 904 can
decrease the magnitude of the positive voltage on red data line
902, which can cause the corresponding red sub-pixel to appear
darker as represented by the downward pointing arrow above red data
line 902. The large negative change in voltage on green data line
904 can increase the magnitude of the negative voltage on blue data
line 906, which can cause the corresponding blue sub-pixel to
appear brighter as represented by the upward pointing arrow above
blue data line 906. In a similar fashion, the change in voltage on
the other green data lines can affect the voltage on their adjacent
red and blue data lines, which can cause these data lines to
brighten or darken in accordance with the illustrated arrows.
[0111] FIG. 9B illustrates the application of voltage to blue data
line 906 in pixel 900, the application of voltage to red data line
912 in pixel 910, the application of voltage to blue data line 926
in pixel 920, and the application of voltage to red data line 932
in pixel 930. The changes in voltage on blue data line 906 and red
data line 912 will be described first.
[0112] With respect to blue data line 906 and red data line 912,
the application of positive voltages to both data lines can change
the polarity of the voltage on both data lines from negative to
positive. The application of voltages to blue data line 906 and red
data line 912 can overwrite any changes in voltage that occurred on
these data lines before time T1. This overwriting is represented by
the absence of arrows above blue data line 906 and red data line
912.
[0113] The large positive change in voltage on blue data line 906
can affect the voltage on green data line 904. In this example, the
large positive change in voltage on blue data line 906 can reduce
the magnitude of the negative voltage on green data line 904, which
can cause the corresponding green sub-pixel to darken as
represented by the downward pointing arrow above green data line
904.
[0114] The large change in voltage on blue data line 906, however,
should have a minimal effect on the voltage on red data line 912.
Because a voltage is applied to both of these data lines at time
T1, both blue data line 906 and red data line 912 can be connected
to different voltage sources. As such, the change in voltage on
blue data line 906 should have a minimal effect on the voltage on
red data line 912 and vice versa. In this way, the write sequences
can be constructed such that the writing of data to adjacent
sub-pixels in adjacent pixels can produce minimal visual artifacts
in the sub-pixels.
[0115] Although the large positive change in voltage on red data
line 912 should have a minimal effect on the voltage on blue data
line 906, this change in voltage can affect the voltage on green
data line 914. In this example, the large positive change in
voltage on red data line 912 can reduce the magnitude of the
negative voltage on green data line 914, which can cause the
corresponding green sub-pixel to appear darker as represented by
the downward pointing arrow above green data line 914.
[0116] The changes in voltage on blue data line 926 and red data
line 932 will be described next. At time T1, negative voltages are
applied to both data lines. These applications of voltage can
overwrite any changes in voltage that occurred on these data lines
before time T1. This overwriting is represented by the absence of
arrows above blue data line 926 and red data line 932.
[0117] The change in voltage on blue data line 926 can affect the
voltage on green data line 924. In this example, the negative
change in voltage on blue data line 926 can reduce the magnitude of
the positive voltage on green data line 924, which can cause the
corresponding green sub-pixel to darken as represented by the
downward pointing arrow above green data line 924.
[0118] Similar to blue data line 906, the change in voltage on blue
data line 926 should have a minimal effect on the voltage on its
adjacent red data line (i.e., red data line 932). Because a voltage
is applied to blue data line 926 and red data line 932 at time T1,
both blue data line 926 and red data line 932 can be connected to
different voltage sources at time T1. As such, the change in
voltage on one data line will not affect the voltage on the other
data line.
[0119] The change in voltage on red data line 932, however, can
affect the voltage on green data line 934. Here, the negative
change in voltage on red data line 932 can reduce the magnitude of
the positive voltage on green data line 934, which can cause the
corresponding green sub-pixel to appear darker as represented by
the downward pointing arrow above green data line 934.
[0120] Referring now to FIG. 9C, negative voltages can be applied
to red data line 902 and blue data line 916, and positive voltages
can be applied to red data line 922 and blue data line 936. The
application of voltages to red data lines 902 and 922 and blue data
line 916 and 936 can overwrite any changes in voltage that occurred
on these data lines before time T2. This overwriting is represented
by the absence of arrows above these data lines.
[0121] With respect to red data line 902, the application of a
negative voltage can affect the voltage on green data line 904. In
this example, the negative change in voltage on red data line 902
can increase the magnitude of the negative voltage on green data
line 904, which can cause the corresponding green sub-pixel to
appear brighter as represented by the upward pointing arrow above
green data line 904. However, green data line 904 also has a
downward pointing arrow because the corresponding green sub-pixel
can darken at time T1. Single sub-pixel offsetting can occur in
this green sub-pixel because the green sub-pixel can both brighten
and darken. In this way, the write sequence for this pixel can be
constructed such that the last application of voltage can offset
any persisting visual artifacts in the pixel.
[0122] In a similar manner, the visual artifacts on the sub-pixel
corresponding to green data line 914 can be offset when a negative
voltage is applied to blue data line 916 in pixel 920. This offset
is represented by the upward and downward pointing arrows above
green data line 914.
[0123] The negative change in voltage on blue data line 916,
however, should have a minimal effect on the voltage on red data
line 922 in adjacent pixel 920. Because voltages are applied blue
data line 916 and red data line 922 at time T2, both data lines are
connected to different voltage sources. As such, the change in
voltage on one data line should have a minimal effect on the
voltage on the other data line.
[0124] Single sub-pixel offsetting can also occur in the green
sub-pixels corresponding to green data lines 924 and 934. With
respect to pixel 920, the positive change in voltage on red data
line 922 can increase the magnitude of the voltage on green data
line 924, which can cause the corresponding green sub-pixel to
appear brighter as represented by the upward pointing arrow above
green data line 924. However, a downward pointing arrow also
appears above green data line 924 as the corresponding green
sub-pixel can darken at time T1. The brightening and darkening of
the green sub-pixel can offset each other. The green sub-pixel
corresponding to data line 934 can be affected in a similar
manner.
[0125] As described above with respect to FIGS. 9A, 9B, and 9C, the
use of GBR and GRB write sequences can yield minimal visual
artifacts in some sub-pixels in which data is concurrently written
to adjacent sub-pixels in adjacent pixels. Moreover, the use of GBR
and GRB write sequences can reduce the presence of any remaining
visual artifacts in the pixel due to the effects of single
sub-pixel offsetting. In this example embodiment, a pattern of GBR
and GRB write sequences in the row of pixels can be a repeating
pattern of alternating one pixel sequenced with GBR and an adjacent
pixel sequenced with GRB. For example, pixel 900 can use a GBR
write sequence, and pixel 910 can use a GRB write sequence. This
pattern of GBR and GRB write sequences can be repeated in pixels
920 and 930, respectively.
[0126] Although the above embodiment is described in relation to
GBR and GRB write sequences in a two-column inversion scheme, a
person of ordinary skill in the art would recognize that other
write strategies may similarly reduce or eliminate visual artifacts
by applying two or more different write sequences in other
inversion schemes.
[0127] In another example embodiment, different write sequences can
be used to reduce or eliminate any errors in luminance by spreading
visual artifacts among different types of sub-pixels. For example,
by distributing artifacts to all three colors of sub-pixels, no
single color (i.e., red, green, or blue) can appear brighter or
darker than the other. For example, visual artifacts can be less
noticeable if all red, green, and blue sub-pixels appear brighter
or darker together, than if only red sub-pixels were affected.
[0128] This example embodiment will be described with respect to
the three-column inversion scheme and four different write
sequences illustrated in FIGS. 10A, 10B, and 10C. These figures
illustrate four adjacent pixels 1000, 1010, 1020, and 1030 along
the same row at different points in time, T0, T1, and T2, during a
scan of the row. Pixel 1000 has a red sub-pixel with a red data
line 1002, a green sub-pixel with a green data line 1004, and a
blue sub-pixel with a blue data line 1006. A demultiplexer 1008
located in the border region of the display can operate the data
lines of pixel 1000. Pixels 1010, 1020, and 1030 have a similar
structure as pixel 1000. As illustrated in FIGS. 10A, 10B, and 10C,
pixels 1000, 1010, 1020, and 1030 use RGB, BGR, BRG, and RBG write
sequences, respectively.
[0129] FIGS. 10A, 10B, and 10C show the applications of voltage to
the data lines for each write sequence, as one of ordinary skill in
the art would understand in light of the disclosure herein. As in
previous figures, the brightenings and darkenings resulting from
the various applications of voltage to the data lines are
represented by the upward and downward pointing arrows above the
data lines.
[0130] In this example embodiment, FIG. 10C can correspond to the
last application of voltage during the update of the row of pixels.
As such, the visual artifacts represented by the upward pointing
arrows in FIG. 10C can persist until this row of pixels is updated
again in the next frame. Here, brightening artifacts can appear on
the sub-pixels corresponding to red data line 1002, green data line
1004, green data line 1014, red data line 1022, blue data line
1026, red data line 1032, and blue data line 1036. In other words,
in the group of four adjacent pixels shown in FIG. 10C, brightening
artifacts can appear in three red sub-pixels, two green sub-pixels,
and two blue sub-pixels. As such, using the RGB, BGR, BRG, and RBG
write sequence can spread visual artifacts among all three colored
sub-pixels. In contrast, if a single RGB write sequence were used
for each pixel, instead of the four different write sequences in
this example embodiment, brightening visual artifacts would appear
on all of the green sub-pixels in the row, and minimal visual
artifacts would appear on red or blue sub-pixels. By spreading the
brightening error in luminance to all three colored sub-pixels in
this example embodiment, the visual artifacts can appear less
noticeable.
[0131] FIG. 11 illustrates circuit diagram of a portion of an
example demultiplexing system including three demultiplexers 1108,
1118, and 1128 according to embodiments of the disclosure. In this
example embodiment, the demultiplexers can be controlled to apply
three different write sequences, RGB, GBR, and BRG. Each
demultiplexer can be connected to one of three pixels 1100, 1110,
and 1120. Pixel 1100 has a red data line 1102, a green data line
1104, and a blue data line 1106. Pixels 1110 and 1120 have a
similar structure as pixel 1100.
[0132] In order to write data to the pixels, a display driver (not
shown) can apply different voltages from different voltage sources
(not shown) to demultiplexers 1108, 1118, and 1128 via data bus
lines 1130, 1140, and 1150. The display driver can transmit three
clock signals, CK1, CK2, and CK3, to the demultiplexers, such that
each demultiplexer can apply the appropriate voltage to the
appropriate data line in accordance with the write sequence for the
demultiplexer's pixel. The write sequence illustrated in FIG. 11,
for example, can use a RGB, GBR, BRG write sequence for pixels
1100, 1110, and 1120, respectively.
[0133] For example, when the first clock signal CK1 is transmitted,
the voltage applied to data bus line 1130 can be the target voltage
for the red sub-pixel of pixel 1100, such that demultiplexer 1108
can apply the target red voltage to red data line 1102 in pixel
1100. Likewise, the voltage applied to data bus lines 1140 and 1150
during CK1 can be the target voltages for the green sub-pixel of
pixel 1110 and the blue sub-pixel of pixel 1120, respectively, such
that demultiplexer 1118 can apply the target green voltage to green
data line 1114 in pixel 1110, and demultiplexer 1128 can apply the
target blue voltage to blue data line 1126 in pixel 1120.
[0134] In a similar fashion, when the second clock signal CK2 is
transmitted, demultiplexer 1108 can apply a voltage to green data
line 1104 in pixel 1100; demultiplexer 1118 can apply a voltage to
blue data line 1116 in pixel 1110; and demultiplexer 1128 can apply
a voltage to red data line 1122 in pixel 1120.
[0135] Finally, when the third clock signal CK3 is transmitted,
demultiplexer 1108 can apply a voltage to blue data line 1106 in
pixel 1100; demultiplexer 1118 can apply a voltage to red data line
1112 in pixel 1110; and demultiplexer 1128 can apply a voltage to
green data line 1124 in pixel 1120.
[0136] In the above example embodiment, a single clock signal can
be used to control a set of demultiplexers to apply voltages to
different types of sub-pixels (e.g., red, green, and blue
sub-pixels) in different pixels. In this way, for example, only
three clock signals may be required to control a system of
demultiplexers to apply three different write sequences.
[0137] One or more of the functions of the above embodiments
including, for example, the additional voltage applications and
overdriving processes can be performed by computer-executable
instructions, such as software/firmware, residing in a medium, such
as a memory, that can be executed by a processor, as one skilled in
the art would understand. The software/firmware can be stored
and/or transported within any non-transitory computer-readable
storage medium for use by or in connection with an instruction
execution system, apparatus, or device, such as a computer-based
system, processor-containing system, or other system that can fetch
the instructions from the instruction execution system, apparatus,
or device and execute the instructions. In the context of this
document, a "non-transitory computer-readable storage medium" can
be any physical medium that can contain or store the program for
use by or in connection with the instruction execution system,
apparatus, or device. The non-transitory computer-readable storage
medium can include, but is not limited to, an electronic, magnetic,
optical, electromagnetic, infrared, or semiconductor system,
apparatus or device, a portable computer diskette (magnetic), a
random access memory (RAM) (magnetic), a read-only memory (ROM)
(magnetic), an erasable programmable read-only memory (EPROM)
(magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD,
DVD-R, or DVD-RW, or flash memory such as compact flash cards,
secured digital cards, USB memory devices, memory sticks, and the
like. In the context of this document, a "non-transitory
computer-readable storage medium" does not include signals.
[0138] FIG. 12 is a block diagram of an example computing system
1200 that illustrates one implementation of an example display
screen according to embodiments of the disclosure. In the example
of FIG. 12, the computing system is a touch sensing system 1200 and
the display screen is a touch screen 1220, although it should be
understood that the touch sensing system is merely one example of a
computing system, and that the touch screen is merely one example
of a type of display screen. Computing system 1200 could be
included in, for example, mobile telephone 136, digital media
player 140, personal computer 144, or any mobile or non-mobile
computing device that includes a touch screen. Computing system
1200 can include a touch sensing system including one or more touch
processors 1202, peripherals 1204, a touch controller 1206, and
touch sensing circuitry (described in more detail below).
Peripherals 1204 can include, but are not limited to, random access
memory (RAM) or other types of memory or non-transitory
computer-readable storage media capable of storing program
instructions executable by the touch processor 1202, watchdog
timers and the like. Touch controller 1206 can include, but is not
limited to, one or more sense channels 1208, channel scan logic
1210 and driver logic 1214. Channel scan logic 1210 can access RAM
1212, autonomously read data from the sense channels and provide
control for the sense channels. In addition, channel scan logic
1210 can control driver logic 1214 to generate stimulation signals
1216 at various frequencies and phases that can be selectively
applied to drive regions of the touch sensing circuitry of touch
screen 1220. In some embodiments, touch controller 1206, touch
processor 1202 and peripherals 1204 can be integrated into a single
application specific integrated circuit (ASIC). A processor, such
as touch processor 1202, executing instructions stored in
non-transitory computer-readable storage media found in peripherals
1204 or RAM 1212, can control touch sensing and processing, for
example.
[0139] Computing system 1200 can also include a host processor 1228
for receiving outputs from touch processor 1202 and performing
actions based on the outputs. For example, host processor 1228 can
be connected to program storage 1232 and a display controller, such
as an LCD driver 1234. Host processor 1228 can use LCD driver 1234
to generate an image on touch screen 1220, such as an image of a
user interface (UI), by executing instructions stored in
non-transitory computer-readable storage media found in program
storage 1232, for example, to control the demultiplexers, voltage
levels and the timing of the application of voltages as described
above to apply different write sequences to write data to a row of
sub-pixels in a display screen during an update of the sub-pixels'
row, although in other embodiments the touch processor 1202, touch
controller 1206, or host processor 1228 may independently or
cooperatively control the demultiplexers, voltage levels and the
timing of the application of voltages. Host processor 1228 can use
touch processor 1202 and touch controller 1206 to detect and
process a touch on or near touch screen 1220, such a touch input to
the displayed UI. The touch input can be used by computer programs
stored in program storage 1232 to perform actions that can include,
but are not limited to, moving an object such as a cursor or
pointer, scrolling or panning, adjusting control settings, opening
a file or document, viewing a menu, making a selection, executing
instructions, operating a peripheral device connected to the host
device, answering a telephone call, placing a telephone call,
terminating a telephone call, changing the volume or audio
settings, storing information related to telephone communications
such as addresses, frequently dialed numbers, received calls,
missed calls, logging onto a computer or a computer network,
permitting authorized individuals access to restricted areas of the
computer or computer network, loading a user profile associated
with a user's preferred arrangement of the computer desktop,
permitting access to web content, launching a particular program,
encrypting or decoding a message, and/or the like. Host processor
1228 can also perform additional functions that may not be related
to touch processing.
[0140] Touch screen 1220 can include touch sensing circuitry that
can include a capacitive sensing medium having a plurality of drive
lines 1222 and a plurality of sense lines 1223. It should be noted
that the term "lines" is sometimes used herein to mean simply
conductive pathways, as one skilled in the art will readily
understand, and is not limited to elements that are strictly
linear, but includes pathways that change direction, and includes
pathways of different size, shape, materials, etc. Drive lines 1222
can be driven by stimulation signals 1216 from driver logic 1214
through a drive interface 1224, and resulting sense signals 1217
generated in sense lines 1223 can be transmitted through a sense
interface 1225 to sense channels 1208 (also referred to as an event
detection and demodulation circuit) in touch controller 1206. In
this way, drive lines and sense lines can be part of the touch
sensing circuitry that can interact to form capacitive sensing
nodes, which can be thought of as touch picture elements (touch
pixels), such as touch pixels 1226 and 1227. This way of
understanding can be particularly useful when touch screen 1220 is
viewed as capturing an "image" of touch. In other words, after
touch controller 1206 has determined whether a touch has been
detected at each touch pixel in the touch screen, the pattern of
touch pixels in the touch screen at which a touch occurred can be
thought of as an "image" of touch (e.g. a pattern of fingers
touching the touch screen).
[0141] In some example embodiments, touch screen 1220 can be an
integrated touch screen in which touch sensing circuit elements of
the touch sensing system can be integrated into the display pixels
stackups of a display.
[0142] Although embodiments of this disclosure have been fully
described with reference to the accompanying drawings, it is to be
noted that various changes and modifications will become apparent
to those skilled in the art. Such changes and modifications are to
be understood as being included within the scope of embodiments of
this disclosure as defined by the appended claims.
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